Date: Fri, 11 Dec 2009 15:05:04 -0000 From: "Steven Hartland" <killing@multiplay.co.uk> To: <freebsd-performance@freebsd.org> Subject: Significant performance regression for increased maxsockbuf on 8.0-RELEASE Message-ID: <AD724D9ED8D64D35A3F0797EB104F763@multiplay.co.uk>
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As noted in the FreeBSD TCP tuning and performance thread here: http://lists.freebsd.org/pipermail/freebsd-performance/2009-December/003909.html There seems to be a significant performance drop when using 8.0 vs 7.0 after digging around this seems to be caused by the use of increased kern.ipc.maxsockbuf Using the default value ( 262144 ) I see the following iperf results: iperf -t 10 -c server1 -w 2.5M -l 2.5M ------------------------------------------------------------ Client connecting to db3, TCP port 5001 TCP window size: 65.0 KByte (WARNING: requested 2.50 MByte) ------------------------------------------------------------ [ 3] local 85.236.96.66 port 50848 connected with 85.236.96.42 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 1.09 GBytes 935 Mbits/sec With anything larger than that the rate drops off significantly e.g. 282144 gives:- iperf -t 10 -c db3 -w 2.5M -l 2.5M ------------------------------------------------------------ Client connecting to db3, TCP port 5001 TCP window size: 65.0 KByte (WARNING: requested 2.50 MByte) ------------------------------------------------------------ [ 3] local 85.236.96.66 port 25867 connected with 85.236.96.42 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 778 MBytes 651 Mbits/sec and 302144 we're down to just under half the baseline / line rate iperf -t 10 -c db3 -w 2.5M -l 2.5M ------------------------------------------------------------ Client connecting to db3, TCP port 5001 TCP window size: 65.0 KByte (WARNING: requested 2.50 MByte) ------------------------------------------------------------ [ 3] local 85.236.96.66 port 12506 connected with 85.236.96.42 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 588 MBytes 492 Mbits/sec Any ideas why using window sizes above 65K results in such poor performance on 8.0? Regards Steve ================================================ This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337 or return the E.mail to postmaster@multiplay.co.uk.
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